JP2008076956A - Method for forming polyimide pattern, article and suspension for hard disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a polyimide pattern containing no photosensitive agent by using a negative resist without using a nonaqueous soluble organic solvent. <P>SOLUTION: The method for forming a polyimide pattern includes: (A) a step of forming a polyimide precursor layer on a substrate; (B) a step of forming a negative resist layer on the polyimide precursor layer; (C) a pattern exposure step of selectively exposing the negative resist layer; (D) a developing step of selectively removing the underlay polyimide precursor layer while or after developing the negative resist layer; (E) a step of at least partially imidizing the patterned polyimide precursor layer to decrease the solubility with a basic aqueous solution or a water-soluble basic substance; and (E) a stripping step of stripping the patterned negative resist layer by using a basic aqueous solution or a water-soluble basic substance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a method for forming a polyimide pattern in which an inexpensive commercially available negative resist can be used without using an expensive photosensitive polyimide in the patterning step, and further, a polyimide pattern that enables the resist to be removed with an aqueous solution. The present invention relates to an article such as an electronic component having a polyimide pattern produced by using these methods, and particularly to a suspension for a hard disk drive.

With the rapid development of semiconductor technology, semiconductor packages have become smaller, more pins, fine pitches, and miniaturized electronic components, and have entered the era of so-called high-density packaging. Along with this, printed wiring boards are also being made thinner and thinner from single-sided wiring to double-sided wiring (Non-Patent Document 1).
In addition, the pattern forming method for forming such wiring / circuits is to form a wiring by etching a metal on a substrate having a layer structure of metal-insulating layer-metal with an acidic solution such as ferric chloride. In order to establish electrical continuity between layers, the insulating layer is removed in a desired shape in a dry state such as a laser or a wet state such as hydrazine (Patent Document 1). A method of forming an insulating layer in a desired shape using polyimide (Patent Document 2) and then forming a wiring by plating in the gap (Preliminary Collection of the 7th Research Discussion Meeting of the Japan Institute of Electronics Packaging) has been performed. .
Electrical products, especially personal computers, are affected by lower prices, and the price of components and parts that use these products is drastically decreasing, and how to make products at low cost is a very big issue.

Currently, the production volume of personal computers is growing rapidly due to the spread of the Internet, etc. The hard disk incorporated in it is also a component called a suspension that supports the head that reads magnetism as the production volume also increases. However, the main product is changing from a wired suspension that connects copper (distribution) wires to stainless steel springs to what is called a wireless suspension in which copper wiring is formed directly on stainless steel springs to accommodate downsizing. is there.
Such a wireless suspension has a structure in which polyimide is applied as an insulating layer on a stainless steel base material, and copper wiring is further formed thereon. In recent years, since higher reliability has been demanded, a wiring protective layer is often provided with polyimide or the like so as to cover the copper wiring.

Since this is a member to which fine vibration is applied because the disk is scanned at a high speed, the adhesion strength between the layers is very important, and strict specifications are required. In addition, since the hard disk is a device for recording information, high reliability is required for reading and writing data, and the specifications are strict against the adhesion strength of wiring, dust such as dust generated from the suspension, and outgas.
In general, a suspension uses a stainless steel layer, a low-expansion insulating layer having the same thermal expansion coefficient as that of the conductor layer, and a wiring protective layer in order to prevent the substrate from warping. Furthermore, management of the hygroscopic expansion coefficient of the insulating layer and the wiring protective layer is also required in order to prevent warping due to environmental changes such as humidity.

The method of forming the polyimide pattern of the insulating layer formed on the stainless steel includes a method using a photosensitive polyimide (Patent Document 3) and a method of etching a polyimide layer formed on the entire surface of the stainless steel with plasma or a chemical solution (Patent Document 4). ) Are disclosed. The above-described method can also be used for a polyimide pattern used as a wiring protective layer.
The method using photosensitive polyimide has the advantage that the process is short and simple, but the polyimide pattern to be formed contains decomposition residues of the photosensitive agent, so that there is a problem that they are released as gas during heating. is there. Furthermore, there is a problem that it is difficult to achieve both of imparting photosensitivity and desired physical properties.
The method of etching a polyimide layer formed on the entire surface of stainless steel with plasma and forming a pattern has the advantage of being able to cope with a relatively wide range of compositions of polyimide, but the etching rate is very low and etching takes time. Therefore, there is a problem that productivity is not good.
The method of etching with a chemical solution has a high etching rate and very high productivity, but has a problem that the molecular structure of the polyimide that can be etched is limited and the range of selection of the composition is small.

  Furthermore, a hole for conducting conduction between layers of a multilayer board is usually drilled with a laser, and it is die-cut into a desired shape with a mold, and an electron using polyimide such as a flexible printed board or multilayer board as an insulating layer Components can also be manufactured using similar polyimide patterning techniques.

JP-A-6-164084 JP-A-4-168441 JP-A-10-12983 JP 2002-240194 A JP-A-6-275511 Iwata, Haraen, “Electronic Materials”, 1996, 35 (10), p.53.

As a polyimide patterning method that has been used for a long time, it is based on the fact that the polyimide precursor polyamic acid is soluble in a basic aqueous solution. After forming a conductive material (resist) film, exposing to a desired pattern and developing with a basic aqueous solution, the positive photoresist and the polyamic acid film are simultaneously patterned, and then the positive photoresist is converted into acetic acid. A technique is disclosed in which a polyimide pattern is obtained by peeling with an organic solvent such as n-butyl to obtain a polyamic acid pattern and then imidizing (Patent Document 5).
Since this method can obtain a pattern formed only of polyimide that does not contain a photosensitizer, the polyimide pattern obtained by this method is highly reliable and does not generate outgas.

However, there has been a problem that an organic solvent is required for stripping the positive photoresist. In general, the basic aqueous solution or the like cannot be used in the peeling step of peeling the positive photoresist because the polyamic acid itself is soluble in the basic aqueous solution. Therefore, there has been a situation that the positive photoresist must be peeled off using an organic solvent that does not dissolve the polyamic acid but dissolves the unexposed positive photoresist.
Such a stripping process using a water-insoluble organic solvent not only has a high load on the natural environment, but is a major obstacle to practical use because of safety measures for workers and waste liquid treatment costs.
Patent Document 5 does not discuss the use of a negative resist instead of a positive resist. This is presumably because the negative resist is a mechanism in which the crosslinking reaction proceeds by exposure to electromagnetic waves or the like and the solubility is lowered, and thus the patterned negative resist after exposure is difficult to peel off.
In Patent Document 5, a positive photoresist is subjected to pattern exposure, developed simultaneously with a polyamic acid coating film, and then heated at 50 ° C. to 90 ° C. for 30 seconds to 20 minutes by a hot plate or oven. However, in order to improve the releasability of the positive photoresist, the residual solvent in the positive photoresist film is made uniform.

  The present invention has been accomplished in view of the above circumstances, and while using an inexpensive negative resist, further enables the resist to be stripped with a water-soluble compound or an aqueous solution thereof, and water or aqueous An object of the present invention is to provide a method for forming a polyimide pattern that does not contain a photosensitizer, to which a solution can be applied, and an article having a polyimide pattern manufactured by using the method, particularly a suspension for a hard disk drive. .

In order to solve the above problems, the present invention provides the following steps (A) to (F):
(A) forming a polyimide precursor layer on the substrate;
(B) forming a negative resist layer on the polyimide precursor layer;
(C) a pattern exposure step for selectively exposing the negative resist layer;
(D) a development step of selectively removing and patterning the underlying polyimide precursor layer after or simultaneously with the development of the negative resist layer;
(E) reducing the solubility in a basic aqueous solution or a water-soluble basic substance by at least partially imidizing the patterned polyimide precursor layer;
(F) A method of forming a polyimide pattern comprising: a peeling step of peeling the patterned negative resist layer using a basic aqueous solution or a water-soluble basic substance.

  According to the present invention, before the (F) peeling step, the (E) the patterned polyimide precursor layer is at least partially imidized to dissolve in a basic aqueous solution or a water-soluble basic substance. By having a process of reducing the property, the patterned negative resist layer can be peeled off using a basic aqueous solution or a water-soluble basic substance while using an inexpensive negative resist, and after the peeling Water or an aqueous solution can be applied to the cleaning step, and a polyimide pattern containing no photosensitive agent can be formed without using a water-insoluble organic solvent in the patterning step.

  In the method for forming a polyimide pattern according to the present invention, it is preferable that the method further comprises (G) a step of polyimidizing the patterned polyimide precursor layer. In the step (E), the polyimide precursor can be converted into a polyimide, but when the polyimide precursor is completely converted into a polyimide in the step (E), the resist layer that is the upper layer of the polyimide precursor is polyimide. Usually, it is preferable to have a step of completely converting the negative resist into a polyimide after peeling because it is often deteriorated by a relatively strong stimulus for making it difficult to peel off.

  In the method for forming a polyimide pattern according to the present invention, it is preferable that a compound that promotes imidization is contained in the polyimide precursor layer in the step (A). When the polyimide precursor layer in the step (A) contains a compound that promotes imidization, the basic aqueous solution or water-soluble basic substance of the patterned polyimide precursor layer (E) is used. In the process of decreasing the solubility, the action of the compound that promotes imidization enables the imidization reaction to be performed with a milder stimulus such as lower temperature heating for a shorter time, and the solubility of the polyimide precursor layer Can be reduced. Therefore, deterioration of the resist layer which is the upper layer of the polyimide precursor can be suppressed.

  In the method for forming a polyimide pattern according to the present invention, it is preferable that the compound that promotes imidization is an amine from the viewpoint of catalytic ability for the imidization reaction and further from the viewpoint of corrosion resistance to the metal layer.

  In the method for forming a polyimide pattern according to the present invention, the amine is preferably an aliphatic amine from the viewpoint of high catalytic effect on the imidization reaction.

  In the polyimide pattern forming method according to the present invention, in the polyimide precursor layer in the step (A), 0.1 to 40 parts by weight of a compound that promotes imidization with respect to 100 parts by weight of the polyimide precursor. It is preferably contained. When the amount is less than 0.1 part by weight, a sufficient catalytic effect cannot be obtained. When the amount exceeds 40 parts by weight, amine tends to remain in the polyimide after imidation, and the physical properties of the polyimide may deteriorate.

  In the method for forming a polyimide pattern according to the present invention, the linear thermal expansion coefficient of the obtained polyimide pattern is 1 ppm / ° C. to 40 ppm / ° C., and the flatness of the finally obtained electronic component, particularly a hard disk drive suspension. Is preferable from the viewpoint of improving the image quality. When the polyimide pattern is laminated with a metal used as a conductor layer or the like, the warpage of the substrate is reduced and the flatness is improved as the linear thermal expansion coefficient is closer to the metal.

  In the polyimide pattern forming method according to the present invention, the resulting polyimide pattern has a hygroscopic expansion coefficient of 1 ppm /% RH to 40 ppm /% RH. It is preferable from the viewpoint that the property can be improved. When the hygroscopic expansion coefficient of the polyimide pattern is large, the substrate may be warped with an increase in humidity due to a difference in expansion coefficient with a metal whose hygroscopic expansion coefficient is almost zero.

  In the method for forming a polyimide pattern according to the present invention, in the (F) peeling step, the negative resist layer can be peeled off with a composition containing an amine so that the resist layer can be peeled uniformly without causing uneven peeling. It is preferable from the point. Furthermore, the amine-containing composition is preferably an amine-containing aqueous solution from the viewpoint of reducing waste liquid treatment costs and improving the working environment.

  In the method for forming a polyimide pattern according to the present invention, the amine in the composition containing the amine in the (F) peeling step is preferably an aliphatic amine from the viewpoint of peelability.

  In the method for forming a polyimide pattern according to the present invention, the amine in the composition containing the amine in the (F) peeling step has a structure having one or more hydroxyl groups in the molecule, so that it can be dissolved in water. From the viewpoint of sex.

  In the method for forming a polyimide pattern according to the present invention, the aqueous solution containing the amine in the (F) peeling step has a concentration of 0.1% by weight to 30% by weight of amine to water. Is preferable from the viewpoint of easy releasability and waste liquid treatment.

  In the method for forming a polyimide pattern according to the present invention, the temperature of the composition containing amine in the (F) stripping step is 0 ° C. or higher and 100 ° C. or lower, and the negative resist layer is stripped. Is preferable from the viewpoint of maintaining a constant value and performing uniform peeling.

  In the method for forming a polyimide pattern according to the present invention, the step (F) is a pre-resist heating before heating the substrate on which the patterned negative resist layer and the patterned polyimide precursor layer are formed. While the process is carried out and the heating temperature is 100 ° C. to 250 ° C., an imidization reaction sufficient to create poor solubility of the polyimide precursor layer in a basic aqueous solution or a water-soluble basic substance is performed, This is preferable from the viewpoint of preventing the deterioration of the negative resist.

  In the method for forming a polyimide pattern according to the present invention, in the step (B), the negative resist layer is preferably formed using a dry film resist. For example, by applying a commercially available negative-type dry film resist, it is not necessary to use a solvent when forming a negative-type resist layer on the polyimide precursor layer, so that the work safety is excellent.

The article according to the present invention is an article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member, and a polyimide pattern formed by using the polyimide pattern forming method according to the present invention. It is what you have.
Since the article according to the present invention has a polyimide pattern formed by using the polyimide pattern forming method according to the present invention and has a polyimide pattern that does not contain a photosensitizer, there is no outgassing and hygroscopic expansion. Since the coefficient and the coefficient of linear thermal expansion can be lowered, problems such as warping of the substrate do not occur, and the reliability is high. Furthermore, it has a feature that it can be manufactured at low cost because it can be processed with an aqueous liquid with a low waste liquid processing cost by using a less expensive polyimide precursor and a negative resist.

  In the article according to the present invention, as one embodiment, it is mentioned that the polyimide pattern is formed on stainless steel or stainless steel subjected to surface treatment. For example, in the hard disk drive suspension according to the present invention, the polyimide pattern is usually formed on stainless steel or a stainless steel pattern subjected to surface treatment. The thickness of the stainless steel used here or the surface-treated stainless steel is preferably 50 μm to 1 μm from the viewpoint of followability to the magnetic disk.

The hard disk suspension according to the present invention has a polyimide pattern formed by using the polyimide pattern forming method according to the present invention.
The hard disk suspension according to the present invention has a polyimide pattern that is formed by using the polyimide pattern forming method according to the present invention, and thus has a polyimide pattern that does not contain a photosensitive agent. Since the linear expansion coefficient and the linear thermal expansion coefficient can be lowered, problems such as warpage do not occur and the reliability is high.

As described above, according to the method for forming a polyimide pattern of the present invention, while using an inexpensive negative resist, it is possible to further remove the resist with a water-soluble compound or an aqueous solution thereof, and to the cleaning process after the peeling. Water or an aqueous solution can be applied, and a polyimide pattern containing no photosensitive agent can be formed without using a water-insoluble organic solvent in the patterning step. Furthermore, since it is possible to form a pattern without being restricted by the chemical structure of the polyimide precursor, polyimide precursors having a wide variety of chemical structures can be used. You can choose.
According to the present invention, since the negative resist can be peeled off with a basic aqueous solution or a water-soluble basic substance without using a water-insoluble organic solvent, the existing equipment used in other processes remains as it is. In addition to being usable, it can reduce the load on the natural environment and solve problems faced in practical use such as worker safety measures and waste liquid treatment costs.
According to the method for forming a polyimide pattern of the present invention, a polyimide pattern that does not contain a photosensitizer can be formed. Therefore, the obtained polyimide pattern has no outgassing and has a hygroscopic linear expansion coefficient and a linear thermal expansion coefficient. And can function as an element imparting heat resistance, insulation and dimensional stability as a permanent film, and is suitable for forming articles such as suspensions for hard disks.

  An article such as a suspension for a hard disk according to the present invention has a polyimide pattern that does not contain a photosensitive agent and is formed by the polyimide pattern forming method according to the present invention. Since the coefficient of thermal expansion can be lowered, defects such as warpage and product malfunction do not occur, and the reliability is high.

The present invention will be described in detail below.
In the present invention, the light used for exposure includes not only electromagnetic waves having wavelengths in the visible and non-visible regions, but also particle beams such as electron beams, and radiation or ionizing radiation that collectively refers to electromagnetic waves and particle beams. It is.
The present invention relates to a polyimide pattern forming method, an article, and a suspension for a hard disk drive. Hereinafter, a polyimide pattern forming method, an article, and a hard disk drive suspension will be described in order.

I. First, a method for forming a polyimide pattern according to the present invention will be described. The method for forming a polyimide pattern of the present invention includes the following steps (A) to (F):
(A) forming a polyimide precursor layer on the substrate;
(B) forming a negative resist layer on the polyimide precursor layer;
(C) a pattern exposure step for selectively exposing the negative resist layer;
(D) a development step of selectively removing and patterning the underlying polyimide precursor layer after or simultaneously with the development of the negative resist layer;
(E) reducing the solubility in a basic aqueous solution or a water-soluble basic substance by at least partially imidizing the patterned polyimide precursor layer;
(F) A stripping step of stripping the patterned negative resist layer using a basic aqueous solution or a water-soluble basic substance.

  According to the present invention, before the (F) peeling step, the (E) the patterned polyimide precursor layer is at least partially imidized to dissolve in a basic aqueous solution or a water-soluble basic substance. By using an inexpensive negative resist, the patterned negative resist layer can be converted into a basic aqueous solution or a water-soluble basic substance (hereinafter referred to as a basic aqueous solution or a water-soluble basic substance). May be referred to as a basic solution), and water or an aqueous solution can be applied to the cleaning step after peeling, without using a water-insoluble organic solvent in the patterning step, A polyimide pattern containing no photosensitizer can be formed. The polyimide pattern of the present invention is a two-dimensional pattern formed of polyimide having a certain thickness.

  The method of forming a polyimide pattern using a polyimide precursor that does not have photosensitivity and a positive or negative resist does not include a photosensitizer in the polyimide precursor, so a photosensitizer is added to the polyimide pattern in the final product. Since it is possible to obtain a pattern formed only of polyimide that does not contain, it is possible to reduce out-gassing coefficient of thermal expansion and coefficient of linear thermal expansion without generating outgas, and have the advantage of high reliability. It is done. However, in the conventional method of forming a polyimide pattern using a polyimide precursor layer having no photosensitivity and a positive photoresist, there is a difference in solubility between the polyimide precursor layer and the positive photoresist. The positive photoresist was peeled off using a water-insoluble organic solvent, which not only has a high impact on the natural environment, but also a major obstacle to practical use due to the safety measures of workers and waste liquid treatment costs. It was a problem. Furthermore, a negative resist is a mechanism in which a crosslinking reaction proceeds due to exposure to electromagnetic waves or the like, resulting in a decrease in solubility. It becomes difficult to remove the resist after exposure and development. The method of using and forming a polyimide pattern has been difficult to adopt.

  In this regard, according to the present invention, before the step of peeling the resist, by using the (E) solubility lowering step, it is possible to peel off with a basic solution while using an inexpensive negative resist, In addition, it becomes possible to apply water or an aqueous solution to the cleaning process after peeling, and a polyimide pattern containing no photosensitizer can be formed. In the present invention, it becomes possible to strip the resist with a basic solution without using a water-insoluble organic solvent, and the existing equipment used in other processes can be used as it is, and the load on the natural environment is reduced. It is possible to obtain a highly reliable polyimide pattern while lowering and solving problems of practical use such as worker safety measures and waste liquid treatment costs.

In the present invention, by using the above-described (E) solubility lowering step before the step of stripping the resist, it is possible to strip with a basic solution while using an inexpensive negative resist as follows. by.
That is, since the negative resist undergoes a crosslinking reaction in the exposed area and becomes insoluble in a weakly basic aqueous solution or an organic solvent, it is usually developed with a weakly basic aqueous solution or an organic solvent such as an aqueous sodium carbonate solution, and the crosslinking reaction The resist is peeled off after development in which the development proceeds, using a strongly basic aqueous solution such as an aqueous sodium hydroxide solution. However, since the polyimide precursor layer patterned in the (D) development step is also dissolved in the basic solution, a polyimide pattern cannot be obtained if it is attempted to peel off with the basic solution as it is.
Therefore, after the (C) pattern exposure step and (D) development step, and before (F) the negative resist peeling step, for example, moderate heating is performed to at least partially imide the polyimide precursor layer. By using the above-mentioned (E) solubility lowering step that lowers the solubility in a basic solution, the solubility in the basic solution between the upper negative resist and the lower polyimide precursor layer is reduced. There is a difference. Therefore, after that, only the patterned negative resist can be peeled off using a basic solution that can remove the crosslinked negative resist but does not dissolve the partially imidized polyimide precursor layer. The pattern of the polyimide precursor layer can be obtained.

  Such a polyimide pattern forming method of the present invention will be specifically described with reference to the drawings. FIG. 1 is a process diagram showing an example of a method for forming a polyimide pattern of the present invention. As shown in FIG. 1A, first, the step (A) for forming the polyimide precursor layer 2 on the substrate 1 is performed. Next, as shown in FIG. 1B, the step (B) for forming a negative resist layer 3 on the polyimide precursor layer 2 is performed. Next, as shown in FIG. 1C, the pattern exposure step (C) is performed in which the negative resist layer 3 is selectively exposed 5 through, for example, a mask 4. As a result, only the exposed negative resist layer 3 changes so as not to dissolve in the developer. Next, as shown in FIG. 1D, only the portion of the polyimide precursor layer 2 under the unexposed portion of the negative resist layer 3 after or simultaneously with the development of the unexposed portion of the negative resist layer 3. The above (D) development step is carried out to selectively remove the film to obtain a patterned negative resist layer 3 ′ and a patterned polyimide precursor layer 2 ′. Next, as shown in FIG. 1E, a basic aqueous solution is obtained by at least partially imidizing the patterned polyimide precursor layer 2 ′ by applying a stimulus 6 such as moderate heating. Or the said (E) solubility reduction process which reduces the solubility with respect to a water-soluble basic substance is performed. As a result, the patterned polyimide precursor layer 2 ′ becomes a polyimide precursor layer 2 ″ with reduced solubility in a basic solution. Depending on the combination of the polyimide precursor layer 2 ′ and the stimulus 6, the basic solution In some cases, the polyimide precursor layer 2 ″ having a reduced solubility in is a polyimide layer that has been completely polyimideized. Next, as shown in FIG. 1 (F), the above-described (F) peeling step of peeling the patterned negative resist layer 3 'with a basic solution is performed. Thereby, a two-dimensional pattern of the polyimide precursor layer 2 ″ is obtained.

  As described above, in the step (F), the polyimide precursor layer 2 ″ may be a completely polyimideized polyimide layer. Usually, however, (G) the patterned polyimide precursor layer 2 is further added. And a step of polyimidizing (not shown). Thereby, a two-dimensional pattern formed of polyimide is obtained.

<(A) Polyimide precursor layer forming step>
In this invention, it has a process (A) which forms a polyimide precursor layer on a board | substrate first.
Examples of the method for forming the polyimide precursor layer on the substrate include, but are not particularly limited to, a method of applying a polyimide precursor layer forming coating solution on the substrate and drying to form a coating film.

As a substrate for forming a polyimide pattern, it can be used without particular limitation as long as it is appropriately selected according to the purpose. For example, a metal such as an alloy such as stainless steel, copper, aluminum, copper alloy, a silicon wafer or a silicon wafer. A semiconductor device having a circuit or element formed thereon, a resin such as polyimide or epoxy resin, or a fiber or particle such as glass, carbon, or aramid resin mixed with such a resin, or copper or Examples are those in which wiring is formed of aluminum or the like.
These substrates are subjected to surface treatments such as chemical treatments such as plating, sputtering, and silane coupling treatment, and physical treatments such as sandblasting for the purpose of improving adhesion, improving reliability, and preventing migration. Also good.

The polyimide precursor used in the present invention is appropriately selected according to the purpose of use of the obtained polyimide pattern, and can be used without any particular limitation. In the step (D), simultaneously with the development of the unexposed portion of the negative resist layer 3, only the portion of the polyimide precursor layer 2 below the unexposed portion of the negative resist layer 3 can be selectively removed. From a possible point, those soluble in a basic solution such as a basic aqueous solution or a water-soluble basic substance are preferable, and examples of a material suitably used include polyamic acid. Specific examples of polyimide precursors that are soluble in basic solutions include those in which a phenol residue is introduced into the carboxyl group of a polyamic acid by an ester bond or the like, a partially imidized polyamic acid, and the like. It is done.
Polyamic acid is not only soluble in a basic solution but also obtained by simply mixing acid dianhydride and diamine in the solution, so it can be synthesized in a single-step reaction, easy to synthesize and at low cost. It is preferable because it is available.

  In addition, for polyamic acid, for applications where the heat resistance and dimensional stability requirements of the finally obtained polyimide are severe, the part derived from acid dianhydride has an aromatic structure, and the part derived from diamine A precursor of wholly aromatic polyimide containing an aromatic structure is preferable. Therefore, the structure derived from the diamine component is also preferably a structure derived from an aromatic diamine.

  Here, the wholly aromatic polyimide precursor is a polyimide precursor obtained by copolymerization of an aromatic acid component and an aromatic amine component, or polymerization of an aromatic acid / amino component, and a derivative thereof. The aromatic acid component is a compound in which all four acid groups forming the polyimide skeleton are substituted on the aromatic ring, and the aromatic amine component is the two amino groups forming the polyimide skeleton. Both are compounds substituted on the aromatic ring, and the aromatic acid / amino component is a compound in which both the acid group and amino group forming the polyimide skeleton are substituted on the aromatic ring. However, as is clear from the specific examples of raw materials described later, it is not necessary for all acid groups or amino groups to be present on the same aromatic ring.

  As a method for producing the polyamic acid of the present invention, a conventionally known method can be applied. For example, (1) A method of synthesizing a polyamic acid as a precursor from an acid dianhydride and a diamine. (2) a compound obtained by reacting a diamino compound or a derivative thereof with a carboxylic acid of an ester acid or an amic acid monomer, which is synthesized by reacting an acid dianhydride with a monovalent alcohol, an amino compound, an epoxy compound, or the like; Examples of the method include, but are not limited to, a method of further reacting an acid dianhydride to synthesize a polyamic acid partially having a functional group introduced therein.

  Examples of the acid dianhydride applicable to the polyamic acid of the present invention include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, and cyclopentane tetracarboxylic dianhydride. Pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4 , 4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, 2, 2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxy) Phenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) ) Methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoro Propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4- Dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) Phenoxy] phenyl} propane Anhydride,

2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4′-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis { 4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarbo Cis) phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) Phenoxy] phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafulpropane dianhydride 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7 -Naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,2,3,4-benzene Tetracarboxylic dianhydride, 3,4,9, 0 Bae Li Ren dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrene tetracarboxylic acid dianhydride, and the like. These may be used alone or in combination of two or more. And as a particularly preferred tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetra Carboxylic dianhydride, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bis (3,4-di Carboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride.

When an acid dianhydride into which fluorine is introduced or an acid dianhydride having an alicyclic skeleton is used as the acid dianhydride to be used in combination, the transparency of the polyimide precursor is improved. Also, rigid acid dianhydrides such as pyromellitic acid anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, etc. When used, the linear thermal expansion coefficient of the finally obtained polyimide becomes small.

  On the other hand, the amine component can also be used alone or in combination of two or more diamines. The diamine component used is not limited, but p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diamino. Diphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4 '-Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4' -Diaminodiph Nylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2 -Di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexa Fluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1 -Phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis ( 3-Aminophenoxy) benzene, 1,3 Bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1, 3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α -Dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis ( 4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dito Trifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2 , 6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-amino) Phenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide,

Bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino) Phenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] ben 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -Α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl ] Diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzen) ) Phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4 , 4′-Dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, , 3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis ( -Aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis ( 2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether,

1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2 -Aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1, 11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohex 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2- Aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2. 1] A diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the above diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group. Can be used.

  Furthermore, depending on the purpose, any one or two or more of the ethynyl group, benzocyclobuten-4′-yl group, vinyl group, allyl group, cyano group, isocyanate group, and isopropenyl group serving as a crosslinking point, Even if it introduce | transduces into some or all of the hydrogen atoms on the aromatic ring of diamine as a substituent, it can be used.

  The diamine can be selected depending on the desired physical properties. If a rigid diamine such as p-phenylenediamine is used, the finally obtained polyimide has a low expansion coefficient. Rigid diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2, 6 as diamines in which two amino groups are bonded to the same aromatic ring. -Diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminoanthracene and the like can be mentioned.

Further, diamines in which two or more aromatic rings are bonded by a single bond, and two or more amino groups are bonded to separate aromatic rings directly or as part of a substituent can be mentioned. Specific examples include benzidine and the like.
Furthermore, in the above diamine, a diamine having a substituent at a position where the amino group on the benzene ring is not substituted and which does not participate in the bond with another benzene ring can also be used. These substituents are monovalent organic groups, but they may be bonded to each other.
Specific examples include 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino. Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned.

  When the finally obtained polyimide is used as an optical waveguide or an optical circuit component, the transmittance for electromagnetic waves having a wavelength of 1 μm or more can be improved by introducing fluorine as a substituent of the aromatic ring.

On the other hand, when a diamine having a siloxane skeleton such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane is used as the diamine, the elastic modulus of the finally obtained polyimide is lowered and the glass transition temperature is lowered. be able to.
Here, the selected diamine is preferably an aromatic diamine from the viewpoint of heat resistance. However, depending on the desired physical properties, the diamine may be an aliphatic diamine or siloxane within a range not exceeding 60 mol%, preferably not exceeding 40 mol%. Non-aromatic diamines such as diamines may be used.

The polyimide precursor used in the present invention preferably has solubility in a basic solution as described above, and specifically, 0.1 wt% of the coating film formed on the substrate at 25 ° C. The dissolution rate with respect to an aqueous solution of tetramethylammonium hydroxide (TMAH) is preferably 100 kg / sec or more. The dissolution rate is more preferably 500 kg / sec or more. Furthermore, the dissolution rate in a 2.38% by weight tetramethylammonium hydroxide aqueous solution, which is a more commonly used developer, is preferably 100 kg / sec or more, and more preferably 500 kg / sec or more. . When the dissolution rate according to the above definition is less than 100 Å / sec, the development time is delayed, workability and productivity are deteriorated, and it is difficult to obtain a solubility contrast between the exposed and unexposed areas.
As a specific procedure for measuring the dissolution rate, a polymer precursor coating film formed on a substrate such as an alkali-free glass was heated to 25 ° C. and stirred with a developer (in this case, 0.1%). The difference between the initial film thickness and the film thickness measured after being immersed in a weight% TMAH aqueous solution or 2.38 wt% TMAH aqueous solution for a certain period of time, rinsed with distilled water and dried The amount of film reduction divided by the time immersed in the developer is the dissolution rate per unit time at 25 ° C.

The weight average molecular weight of the polyimide precursor is preferably in the range of 3,000 to 1,000,000, more preferably in the range of 5,000 to 500,000, although it depends on the application. More preferably, it is in the range of 1,000,000 to 500,000. When the weight average molecular weight is less than 3,000, it is difficult to obtain sufficient strength when a coating film or film is used. In addition, the strength of the film is reduced when heat treatment is performed to obtain polyimide. On the other hand, when the weight average molecular weight exceeds 1,000,000, the viscosity increases and the solubility decreases, so that it is difficult to obtain a coating film or film having a smooth surface and a uniform film thickness.
The molecular weight used here is a molecular weight obtained by a known method, and is exemplified by a value in terms of polystyrene by gel permeation chromatography (GPC). In this case, the molecular weight of the polyimide precursor itself may be used, or the molecular weight after chemical imidization treatment with acetic anhydride or the like may be used.

(A) It is preferable to contain the compound which accelerates | stimulates imidation in the polyimide precursor layer in a process. The compound that promotes imidization refers to a compound having a catalytic action that promotes the polyimide formation reaction of the polyimide precursor. When the polyimide precursor layer in the step (A) contains a compound that promotes imidization, (E) the solubility of the patterned polyimide precursor layer in a basic solution described later is reduced. In the process of making it, it becomes possible to imidize a polyimide precursor layer by a mild stimulus and to reduce the solubility with respect to a basic solution by the effect | action of the compound which accelerates | stimulates imidation. Therefore, in such a case, it is possible to prevent the negative resist layer, which is the upper layer of the polyimide precursor, from being deteriorated, and it is possible to use a weakly irritating chemical solution such as an aqueous solution having a low concentration. It is possible to suppress the substrate and the polyimide precursor pattern from being damaged.
That is, in the step (E) described later, the higher the imidization rate, the better the resistance of the polyimide precursor pattern to the basic solution. However, the strong stimulus for increasing the imidation rate, on the other hand, is a negative resist. May deteriorate, and the solubility of the negative resist layer in the basic solution may be reduced. When the negative resist layer deteriorates, it becomes necessary to use a stronger basic solution or to peel off under extreme conditions. If the negative resist layer is peeled off under such extreme conditions, the pattern of the substrate and the polyimide precursor may be damaged. It is preferable to imidize the polyimide precursor layer under mild conditions so as to suppress the deterioration of the resist to lower the solubility in a basic solution.

Examples of the compound that promotes imidization contained in the polyimide precursor layer include basic substances. Among them, amines that are organic substances are preferable because of their high catalytic ability.
Among them, aliphatic amines are particularly preferable because they have a high catalytic effect on the imidation reaction of the polyimide precursor regardless of the series. The aliphatic amine refers to a compound in which a hydrogen atom of ammonia is substituted with a hydrocarbon group, and all the bonds extending from a carbon atom having a bond with nitrogen of the hydrocarbon group are single bonds. The hydrocarbon group may be linear, branched or cyclic, and may have a substituent or a hetero bond in the structure. These include primary amines such as n-butylamine, benzylamine, amylamine, hexylamine and octylamine, secondary amines such as diethylamine, dipropylamine, diisopropylamine, dibutylamine and dimethylpiperidine, ethylenediamine , Propylene diamine, trimethylene diamine, triethylene diamine (1,4-diazabicyclo [2.2.2] octane), alkylene diamines such as tetramethylene diamine, pentamethylene diamine and hexamethylene diamine, triamines such as diethylene triamine, and other tetramines Compounds and amines such as benzylamine are exemplified, but are not particularly limited as long as the effects of the present invention can be achieved.

  In the polyimide precursor layer in the step (A), the compound for promoting imidization with respect to 100 parts by weight of the polyimide precursor is 0.1 to 40 parts by weight, and further 0.5 to 30 parts by weight. , Preferably. When the compound that promotes imidization is less than 0.1 part by weight based on 100 parts by weight of the polyimide precursor, the effect of promoting the imidization reaction is insufficient. On the other hand, when the compound that promotes imidization with respect to 100 parts by weight of the polyimide precursor exceeds 40 parts by weight, the compound that promotes imidization tends to remain in the polyimide after imidation, and the physical properties of the polyimide are May decrease.

  The compound that promotes imidization contained in the polyimide precursor layer in the step (A) is preferably used from the viewpoint of reliability so as not to remain in the finally obtained polyimide pattern. Therefore, the compound that promotes imidization is preferably decomposed or volatilized in the step of imidization. Specifically, the compound that promotes imidization has a temperature (5% weight reduction temperature) when it is reduced by 5% from the initial weight by heating (25% to 350 ° C), preferably 25 ° C to 250 ° C. It is preferable that the temperature is 0 ° C. because the compound that promotes imidization can be decomposed or volatilized by heating so that it does not remain in the polyimide after imidization.

  In the polyimide precursor layer in the step (A) of the present invention, various organic or inorganic low molecules or polymers are added to impart processing characteristics and various functionalities unless the effects of the present invention are impaired. You may mix | blend a compound. For example, dyes, surfactants, leveling agents, plasticizers, fine particles and the like can be used. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicate, and these may have a porous or hollow structure. The function or form includes pigments, fillers, fibers, and the like.

  The coating liquid in the case where the polyimide precursor layer is formed by applying a polyimide precursor layer forming coating liquid on the substrate and drying to form a coating film, the polyimide precursor as an essential component, and the like. Are mixed and dissolved in a solvent to prepare. The solvent is not particularly limited as long as the polyimide precursor is an essential component and is a good solvent for other components. For example, N-methyl-2-pyrrolidinone, dimethylacetamide, dimethylformamide, γ-butyrolactone can be used. , Γ-valerolactone, dimethyl sulfoxide and the like.

  As a coating method, a known method such as dip coating, spin coating, die coating, roll coating, slit coating or the like can be used as appropriate.

  The drying method for removing the solvent from the film coated with the coating liquid includes heating, and a known apparatus / method such as an oven or a hot plate can be used. The heating temperature is preferably in the range of 80 ° C to 140 ° C.

  The thickness of the polyimide precursor layer is appropriately selected depending on the use of the obtained polyimide pattern and is not particularly limited, but is usually formed to be 0.5 μm to 100 μm.

<(B) Step of forming a negative resist layer on the polyimide precursor layer>
As a method of forming a negative resist layer on the polyimide precursor layer, a negative resist layer forming coating solution is applied on the polyimide precursor layer formed in the step (A) and dried. Although the method of forming a coating film is mentioned, it is not specifically limited. A method in which a negative resist layer in the form of a solid or gel-like film at room temperature is bonded onto a substrate, such as a dry film resist. Since a negative resist layer can be formed without using a solvent, the use of a dry film resist is preferable from the viewpoint of improving the working environment.

A negative resist is a material in which the solubility of an irradiated portion in a developer changes from soluble to insoluble or hardly soluble by irradiation with electromagnetic waves such as ultraviolet rays. The negative resist can be patterned in an exposed part and an unexposed part by irradiating electromagnetic waves such as ultraviolet rays through a desired exposure mask (pattern), and the unexposed part is eluted in the developer.
Specifically, the negative resist is composed of a polymer binder, a monofunctional and / or polyfunctional monomer, a photopolymerization initiator, and other additives. As the negative resist layer forming coating solution, a mixed solution of these components is usually used. The dry film is produced by applying these mixed solutions to a substrate such as a film.

The polymer binder used in the negative resist is mixed for the purpose of imparting film-forming properties that maintain the form of a negative resist coating film or dry film, or for the purpose of imparting developability.
As the polymer binder, an acrylic resin is mainly used, but there are no particular limitations on polyester, polyamide, polyether, polyallylamine, and the like. Moreover, when using as a dry film, since the shape must be maintained, the weight average molecular weight of the polymer binder is preferably 6000 or more, and the weight average molecular weight is 100,000 or less from the viewpoint of developability. Although it is preferably used, it is not particularly limited. The weight average molecular weight is generally determined by a gel permeation chromatography (common name: GPC) relative to standard polystyrene, but if it is not soluble and cannot be measured by GPC, other known methods can be used. Can be measured.

In the case of alkaline development, an acidic functional group is introduced into the polymer binder in order to impart developability with an aqueous solution whose pH is adjusted.
Moreover, in order to improve the heat resistance and mechanical characteristics of the final cured product, a photocurable substituent may be introduced. Examples of the photocurable substituent include an ethylenically unsaturated bond-containing group and an oxetanyl group.
These photocurable substituents exhibit photocurability by the action of additives such as a photoradical generator, photoacid generator, and photobase generator.

Polyfunctional monomers and monofunctional monomers dissolve negative resists by reacting with polymer binders and other polyfunctional monomers to form a cross-linked structure by radicals generated by photopolymerization initiators upon irradiation with ultraviolet rays. It works to reduce sex.
The polyfunctional monomer and the monofunctional monomer are low molecular weight components having one or more curable substituents, and the molecular weight or number average or weight average molecular weight is preferably 100 or more and 10,000 or less, and 100 or more and 5,000 or less. Is more preferable. If it is less than 100, the curable component volatilizes during drying, and the component ratio of the resin composition changes. In addition, the solubility decreases when the molecular weight is large.
Examples of the curable substituent contained in the polyfunctional monomer and the monofunctional monomer include an ethylenically unsaturated bond-containing group and an oxetanyl group.

  Specifically, 1,6-hexanediol di (meth) acrylate, 1,4-cyclohexanediol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polyoxyethylene polyoxy Polyoxyalkylene glycol di (meth) acrylate such as propylene glycol di (meth) acrylate, 2-di (p-hydroxyphenyl) propane di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, Polyoxypropyltrimethylolpropane tri (meth) acrylate, polyoxyethyltrimethylolpropane triacrylate, dipentaerythritol penta (meth) acrylate, trimethyl Roll propane triglycidyl ether tri (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, 2,2-bis (4-methacryloxypentaethoxyphenyl) propane, and polyfunctional (meth) acrylate containing urethane group There are, but not limited to, polyfunctional methacrylate or acrylate containing bisphenol A in the structure.

  The photopolymerization initiator absorbs electromagnetic waves, particularly ultraviolet rays, and generates radicals by cleaving and / or removing hydrogen from other molecules. For example, 2-ethylanthraquinone, octaethylanthraquinone, 1, 2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-Fe Quinones such as nantraquinone, 2-methyl-1,4-naphthoquinone, 2,3-dimethylanthraquinone, 3-chloro-2-methylanthraquinone, benzophenone, Michler's ketone [4,4′-bis (dimethylamino) benzophenone], 4,4'-bis (diethylamino ) Aromatic ketones such as benzophenone, benzoin, benzoin ethyl ether, benzoin phenyl ether, benzoin ethers such as methyl benzoin, ethyl benzoin, benzyl dimethyl ketal, benzyl diethyl ketal, 2- (o-chlorophenyl) -4,5- Biimidazole compounds such as diphenylimidazolyl dimer, combinations of thioxanthones and alkylaminobenzoic acid, such as ethylthioxanthone and ethyl dimethylaminobenzoate, 2-chlorothioxanthone and ethyl dimethylaminobenzoate, isopropylthioxanthone and ethyl dimethylaminobenzoate A combination of 2- (o-chlorophenyl) -4,5-diphenylimidazolyl dimer and Michler's ketone, 9-phenyl Acridines such as klysine, oxime esters such as 1-phenyl-1,2-propanedione-2-o-benzoyloxime, 1-phenyl-1,2-propanedione-2- (ο-ethoxycarbonyl) oxime, etc. There is no particular limitation.

  In addition, examples of the additive include, but are not limited to, a dye that enhances the absorption efficiency of irradiated electromagnetic waves, a plasticizer that gives flexibility to the negative resist and the dry film itself, and the like.

  The negative resist used in the present invention is preferably one that can be developed and stripped with a basic solution, but is not particularly limited. For example, negative resists that can be developed and peeled off with a basic aqueous solution are commercially available in the form of dry films such as Sunfort Series (trade name) manufactured by Asahi Kasei Kogyo Co., Ltd. Is mentioned.

When the negative resist is a dry film type, the method for adapting to the substrate is not particularly limited. However, when a laminating method is used, a known laminating method such as a roll press or a surface press can be used.
When the rigidity of the substrate to be used is low, it is preferable to use the surface pressing method. When laminating by roll press, the substrate may be warped when processed for each sheet, and if the substrate is warped, a large shift in alignment occurs after exposure. Therefore, when laminating a dry film resist, it is preferable to use a surface press to produce a product as designed with high accuracy.
As conditions for laminating the dry film, the temperature is preferably in the range of 20 to 100 ° C., and the pressure is preferably in the range of 0.05 to 0.3 MPa (0.5 to 3 Kgf / cm ² ).

Further, if air bubbles are mixed when laminating, the portion becomes poor in adhesion, and the pattern shape of the polyimide precursor is poor. For this reason, laminating under reduced pressure is effective.
When the unevenness on the substrate is large, it is preferable to perform the atmosphere at the time of lamination at a vapor pressure of 1.0 × 10 ⁻¹ Pa (50 mmHg) or less because it is necessary to reduce the mixing of bubbles. However, when the pattern is relatively large and the wiring interval and the like are large, air bubbles may not be mixed even if the pressure is not reduced. In that case, the pressure does not necessarily have to be reduced.
The vacuum suction time is adjusted according to the size of the sheet to be processed, but the time is set so that no bubbles remain between the dry film resist and the sheet during pressure bonding.

In addition, when laminating in a reduced pressure state, using a dry film having fine irregularities on the surface and laminating with the irregularities facing the substrate side is very effective in removing bubbles.
As for the unevenness | corrugation given to the dry film resist surface, it is preferable that the surface roughness Rz is the range of 0.5 micrometer-50 micrometers. Even if the method of forming the unevenness is carried out by embossing after making the mixed solution of the constituent components into a dry film state, the mixed solution of the constituent components is applied to the film with the unevenness in advance and dried to make the unevenness. However, the method is not particularly limited.

When a negative resist forming coating solution is applied on the polyimide precursor layer and dried to form a coating film to form a negative resist layer, the coating solution is a component of the negative resist forming component. In addition, other components are appropriately blended and dissolved in a solvent. Care should be taken in selecting the solvent. That is, it is necessary to select a solvent that does not dissolve the underlying polyimide precursor layer. Specifically, it is necessary to select a solvent that does not dissolve 3.0% by weight or more of the polyimide precursor as a lower layer with respect to the solvent.
As a coating method, the same method as mentioned in the step (A) can be used.

  The drying temperature after coating is preferably 60 ° C to 120 ° C, more preferably 70 ° C to 100 ° C. If it is less than 60 ° C., the solvent does not volatilize sufficiently and remains in the film or takes time for drying, which is not preferable. If the temperature exceeds 120 ° C., the photosensitive agent and additives in the negative resist are gradually decomposed, which is not preferable.

  The thickness of the negative resist layer is not particularly limited, but is usually formed to be 0.5 μm to 100 μm.

<(C) Pattern exposure process>
In the step (C), the negative resist layer is selectively exposed. Thereby, only the exposed part of the negative resist layer changes the solubility in the developer to insoluble or hardly soluble.
Examples of the selective exposure method include a projection exposure method through a mask. The exposure method and exposure apparatus used in the exposure process are not particularly limited, and may be contact exposure or indirect exposure, and any known means such as a stepper, scanner, aligner, contact printer, laser, and electron beam drawing can be used. .

<(D) Development step>
In the step (D), the polyimide precursor layer under the unexposed portion of the negative resist layer 3 after or simultaneously with the development of the unexposed portion of the negative resist layer 3 subjected to pattern exposure in the step (C). Only the portion 2 is selectively removed to obtain a patterned negative resist layer 3 ′ and a patterned polyimide precursor layer 2 ′.

The development of the negative resist layer is preferably carried out under the recommended conditions using a developer corresponding to the negative resist used, and is not particularly limited.
However, as described above, from the viewpoint of waste disposal, development with a basic aqueous solution is preferable as in the later-described (G) peeling step. In particular, development with an aqueous organic alkali solution is preferred, and among them, an aqueous tetramethylammonium hydroxide solution is preferred. The concentration is preferably 0.01% to 70% by weight, particularly preferably 0.1% to 20% by weight. If it is less than 0.01% by weight, the unexposed area of the negative resist is poorly soluble and cannot be developed well. If it exceeds 70% by weight, the exposed area will swell and it will be difficult to obtain the desired pattern.

The developing method may be a dip method, a spray method, or a submerged spray method, and is not particularly limited.
When the polyimide precursor layer under the negative resist is dissolved in the developer used at this time, it is possible to selectively remove the negative resist layer and the polyimide precursor layer at the same time, Process can be reduced. Also in this sense, development of a negative resist with an inorganic or organic alkaline aqueous solution is effective after using a polyimide precursor soluble in a basic aqueous solution.

  When the polyimide precursor does not dissolve in the negative resist developer, the polyimide precursor is used after the development of the negative resist using a liquid that does not dissolve the obtained negative resist pattern but dissolves the polyimide precursor. The film pattern is formed. In that case, the difference between the dissolution rate of the negative resist pattern and the dissolution rate of the polyimide precursor with respect to the solution used for forming the pattern of the polyimide precursor is 50 times or more, and the larger the polyimide precursor is better.

<(E) Solubility reduction step>
In the step (E), the solubility in a basic aqueous solution or a water-soluble basic substance is lowered by at least partially imidizing the polyimide precursor layer patterned in the development step (D). The basic aqueous solution or the water-soluble basic substance will be described in detail in the next step (F).
By reducing the solubility of the patterned polyimide precursor layer in the basic solution, a difference in solubility in the basic solution can be made between the upper negative resist layer and the upper negative resist layer. Only the basic solution can be peeled off. As the difference in solubility in the basic solution, the dissolution rate of the negative resist pattern after performing the step (E) with respect to the basic solution used is the polyimide precursor after performing the step (E). The dissolution rate of the pattern is preferably 10 times or more, more preferably 30 times or more. More specifically, for example, the dissolution rate of the polyimide precursor pattern after the step (E) in a 0.1 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 25 ° C. is less than 1000 kg / sec. Further, the dissolution rate in a 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 25 ° C. is preferably less than 1000 kg / sec.

  A polyimide precursor that is soluble in a basic aqueous solution or a water-soluble basic substance is preferably used because of the advantages in the above-described steps, but even such an alkali-soluble polyimide precursor is converted into a polyimide. The solubility of the polyimide precursor in a basic aqueous solution or a water-soluble basic substance is lowered. Therefore, in the present invention, as a method for reducing the solubility of the polyimide precursor layer in a basic aqueous solution or water-soluble basic substance, an upper negative resist layer is used for a certain basic aqueous solution or water-soluble basic substance. Is dissolved, but the polyimide precursor layer is at least partially imidized to such an extent that the polyimide precursor layer does not dissolve.

The imidation ratio in the polyimide precursor layer is appropriately adjusted depending on the solubility of the polyimide precursor used in the basic solution and is not particularly limited, but is usually 1% or more, and further 5% or more. It is preferable. The imidation ratio here is about the polyimide precursor as a raw material used in the step (A) in an infrared absorption spectrum (for example, measured using a Fourier transform infrared spectrophotometer FT-IR610 manufactured by JASCO Corporation). , When the peak area of the carbonyl group peak of the amide bond derived from the precursor (usually around 1663 cm ⁻¹ ) is 1, the amount of decrease in the peak area in the heating process is calculated in terms of the imidization rate. . The state of the polyimide precursor layer in the step (A) is 0% imidation, and the imidation rate is 100% when the peak completely disappears. From the viewpoint of reducing the solubility of the polyimide precursor pattern in the basic solution, the polyimide reaction may be performed until the imidization rate becomes 100%. In addition, if imidization is completed, there is an advantage that the process of imidizing after removing the negative resist need not be performed, and the process can be greatly shortened. On the other hand, if the heating is performed at a high temperature for a long time in order to obtain an imidization rate of 100%, the upper negative resist layer deteriorates and peels off under extreme conditions. As a result, the substrate and the polyimide precursor May damage the pattern.
In addition, when using the polyimide precursor partially imidized from the beginning, the imidation rate is calculated by setting the initial value to 0%.

As a method for partially imidizing the polyimide precursor layer, for example, moderate heating can be mentioned. The process of partially imidizing by heating can be performed by an oven, a hot plate, a conveyor-type infrared furnace, or the like. The temperature condition in this case can be appropriately selected according to the polyimide precursor used, but is usually in the range of 100 ° C to 450 ° C, preferably in the range of 140 ° C to 250 ° C. When a compound that promotes imidization is contained in the polyimide precursor layer in the step (A), the solubility can be lowered by performing imidization at a lower temperature, and the temperature condition is 120 ° C. It can select in the range of -230 degreeC. If the temperature is too low, an imidization reaction sufficient to create poor solubility in a basic aqueous solution or a water-soluble basic substance cannot be performed. If the temperature is too high, the negative resist is likely to deteriorate, May be difficult to dissolve in the acidic solution.
In addition, the heating temperature of the heating conditions in this invention says the temperature of the location where what is heated is in contact.

  The heating and holding time at the heating temperature needs to be appropriately set depending on the heating temperature and the heating technique, but is preferably 1 second to 30 minutes, preferably 5 seconds to 20 minutes. If the heating and holding time is too short, the effect of heating is difficult to be exhibited, and the polyamic acid is easily dissolved in the liquid used for peeling the negative resist which is the next step. If the heating and holding time is too long, the productivity is increased. Decreases.

  Furthermore, it is preferable that the heating step is performed in an inert atmosphere from the viewpoint of suppressing deterioration of the negative resist. Specific examples of the inert atmosphere in this case include reduced pressure, nitrogen atmosphere, and rare gas atmosphere such as argon and helium.

  Depending on the combination of the polyimide precursor to be used and the negative resist, there may be a case where imidization can be performed completely when the imidization reaction is performed in the (E) solubility reduction step. In this case, there is a merit that the polyimide forming step after the (G) negative resist removal described later can be omitted, and the process can be greatly shortened.

<(F) Peeling step>
In the step (F), the patterned negative resist layer is peeled off using a basic aqueous solution or a water-soluble basic substance.
In the present invention, in order to reduce the load on the natural environment and solve practical problems such as worker safety measures and waste liquid treatment costs, a basic aqueous solution or a water-soluble solution is used without using a water-insoluble organic solvent. The negative resist is removed with a basic substance. Since peeling is performed with a basic aqueous solution or a water-soluble basic substance, there is an advantage that the equipment used in the development step (D) can be used as it is. Further, the substrate rinsing and cleaning steps after peeling can be performed with water or an aqueous solution.
As the peeling of the negative resist layer, there are a case where the negative resist is swollen and peeled, and a case where both are dissolved and peeled together.

  As said basic solution, although the polyimide precursor pattern after performing a process (E) has low solubility, it is necessary to select and use a solution with high solubility with respect to a negative resist pattern suitably. As a guideline for selecting such a basic solution, the dissolution rate of the negative resist pattern after the step (E) is equal to the dissolution rate of the polyimide precursor pattern after the step (E). It may be mentioned to select a basic solution having a dissolution rate of 10 times or more, more preferably 100 times or more.

  Among the basic solutions used in the present invention, examples of the basic aqueous solution include inorganic or organic alkaline aqueous solutions, and organic alkaline aqueous solutions are particularly preferable from the viewpoint of waste liquid treatment. Among these, an aqueous solution of a water-soluble amine is preferable. Here, the water-soluble amine means a primary to quaternary amine that can be dissolved in distilled water at a concentration of 0.1 mol / L or more. From the viewpoint of releasability, aliphatic primary, secondary and tertiary amines are preferred, and from the viewpoint of solubility in water, primary, secondary and tertiary amines containing one or more hydroxyl groups in the molecule are preferred. . Aliphatic primary, secondary and tertiary amines containing one or more hydroxyl groups in the molecule are more preferred. These primary to quaternary amines may have a substituent, and examples of the aliphatic amine having a hydroxyl group include ethanolamine, N, N, -dimethylethanolamine, propanolamine, and triethanolamine. However, it is not particularly limited.

  The concentration of the water-soluble amine in water is preferably between 0.01% by weight and 30% by weight, and more preferably between 0.5% and 20% by weight. If it is less than 0.01% by weight, the solubility of the exposed portion of the negative resist is poor and the negative resist pattern cannot be peeled off successfully. If it exceeds 30% by weight, the polyamic acid pattern will swell or elute, making it difficult to obtain the desired pattern.

Of the basic solutions used in the present invention, the water-soluble basic substance means an organic compound having a water-soluble pH greater than 7, specifically, a primary, secondary, tertiary amine, or A quaternary amine (ammonium compound) is mentioned. Here, the water solubility of the water-soluble basic substance of the present invention means that an aqueous solution can be obtained at a concentration of 1% by weight or more and 90% by weight or less at 25 ° C., preferably 5% by weight or more and 60% by weight or less. This means that a concentrated aqueous solution is obtained. In order to peel off the negative resist layer whose solubility has been greatly reduced by stimulation such as heating in the step (E), peeling with the water-soluble basic substance is preferable. Specifically, primary to quaternary amines that are liquid at any temperature between 0 ° C. and 100 ° C. are used, and primary to quaternary aliphatic amines are preferred. Since aliphatic amines are generally highly basic, they are more excellent in peelability.
These primary to quaternary amines may have a substituent, and an aliphatic amine having a hydroxyl group is particularly effective for peeling. Specific examples include amines described in the above basic aqueous solution, but are not particularly limited.

  When peeling with a basic aqueous solution or a water-soluble basic substance, in addition to basic substances such as amine-containing compositions, surfactants, antioxidants, chemicals that suppress damage to the substrate, etc. You may use the composition which mixed these various additives as stripping solution. These various additives are preferably added at a lower concentration than the concentration of the inorganic or organic basic substance so as not to inhibit the function of the inorganic or organic basic substance.

Usually, the stripping is performed at a temperature at which the stripping solution can exist in a liquid state. However, in order to shorten the time required for stripping, it is preferable to raise the temperature of the stripping solution. The temperature of the composition containing a basic substance such as amine is usually 0 ° C. or higher and 100 ° C. or lower, and the negative resist layer is peeled off. When the stripping solution is an aqueous solution, it is more preferably 10 ° C to 85 ° C, and more preferably 20 ° C to 70 ° C. If it is less than 0 ° C, it takes time for peeling, and if it exceeds 95 ° C, the stripping solution tends to volatilize, the concentration of the content tends to change, and further damages the pattern of the polyimide precursor. There is a problem that it becomes easy.
The peeling method may be a dip method, a spray method, or a submerged spray method, and is not particularly limited.

<(G) Polyimidation process>
In step (G), (F) the patterned polyimide precursor layer 2 ″ is polyimideized.
Before imidizing the patterned polyimide precursor layer 2 ″, it may be washed with distilled water or warm water as necessary.

Examples of the imidization method include a method of heating, a method of contacting with a catalyst, a method of heating after being immersed in a catalyst solution, and the like.
In the case of imidization by heating, it is preferable to perform heat treatment at a temperature between 150 ° C. and 400 ° C., preferably at a temperature between 180 ° C. and 370 ° C. for 1 minute to 300 minutes. A known method can be used.
Further, this heating step is preferably performed in an inert atmosphere when the substrate contains a metal that is easily oxidized from the viewpoint of preventing oxidation of the metal. Specific examples of the inert atmosphere in this case include reduced pressure, nitrogen atmosphere, and rare gas atmosphere such as argon and helium.

The polyimide pattern thus obtained has a 5% weight loss temperature measured in nitrogen of preferably 250 ° C. or higher, more preferably 300 ° C. or higher. In particular, when used in applications such as electronic parts that pass through the solder reflow process, if the 5% weight loss temperature is less than 300 ° C, defects such as bubbles occur due to the decomposition gas generated in the solder reflow process. There is a fear.
Here, the 5% weight reduction temperature is the time when the weight of the sample is reduced by 5% from the initial weight when the weight loss is measured using a thermogravimetric analyzer (in other words, the sample weight becomes 95% of the initial weight). Temperature). Similarly, the 10% weight reduction temperature is a temperature at which the sample weight is reduced by 10% from the initial weight.

The polyimide pattern thus obtained preferably has a linear thermal expansion coefficient of 1 ppm / ° C. to 40 ppm / ° C. from the viewpoint of dimensional stability. In particular, when a film is formed on a metal such as copper or stainless steel in a manufacturing process for electronic parts or the like, it is more preferably 1 ppm / ° C. to 20 ppm / ° C. from the viewpoint of adhesion and warpage of the substrate. Here, since the linear thermal expansion coefficient of the polyimide pattern in the present invention can be regarded as an equivalent value regardless of the size of the pattern, if the polyimide pattern itself cannot be measured due to the size of the pattern, A polyimide film for evaluating linear thermal expansion coefficient that has undergone a similar pattern forming process may be prepared and evaluated using the polyimide precursor that is used. In addition, the linear thermal expansion coefficient in this invention can be calculated | required with a thermomechanical analyzer (TMA). Using a thermomechanical analyzer (for example, Thermo Plus TMA8310 (manufactured by Rigaku Corporation), the heating rate is 10 ° C./min, and the tensile load is 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample is the same. .

  The polyimide pattern thus obtained preferably has a hygroscopic expansion coefficient of 1 ppm /% RH to 40 ppm /% RH from the viewpoint of dimensional stability. In particular, it is more preferably 1 ppm /% RH to 20 ppm /% RH from the viewpoint of adhesion and warpage of the substrate in the manufacturing process of electronic parts and the like. Here, since the hygroscopic expansion coefficient of the polyimide pattern in the present invention can be regarded as an equivalent value regardless of the size of the pattern, when the polyimide pattern itself cannot be measured due to the size of the pattern, it is used for the polyimide pattern. A polyimide film for evaluating hygroscopic expansion coefficient that has undergone the same pattern forming process may be prepared and evaluated using the polyimide precursor that has been prepared. The hygroscopic expansion coefficient in the present invention refers to the average rate of change (displacement / initial length) of the length of material per 1% Rh when the humidity is changed from 30% Rh to 70% Rh at 25 ° C.

II. Articles such as suspension for hard disk The article according to the present invention is an article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member, and uses the polyimide pattern forming method according to the present invention. It has a formed polyimide pattern.
The suspension for a hard disk according to the present invention has a polyimide pattern formed by using the method for forming a polyimide pattern according to the present invention.
Since an article such as an electronic component such as a hard disk suspension according to the present invention has a polyimide pattern formed by using the polyimide pattern forming method according to the present invention, it has a polyimide pattern that does not contain a photosensitive agent. Therefore, the moisture absorption linear expansion coefficient and the linear thermal expansion coefficient can be lowered, so that problems such as warpage do not occur and the reliability is high.

  The article according to the present invention having a polyimide pattern formed by using the polyimide pattern forming method according to the present invention is any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member, There is no particular limitation. For example, a semiconductor device having a polyimide pattern in an insulating layer of a flexible printed board, a wiring protective layer, an insulating layer of a semiconductor mounting board, a wiring protective layer, an insulating layer of a semiconductor device, a surface protective film, etc. is exemplified. In addition to electronic components such as hard disk suspensions and chip scale package substrates, optical circuit components such as waveguides and cladding layers of optical circuit components can be used.

An electronic component which is one of the articles according to the present invention will be specifically described with reference to the hard disk suspension according to the present invention. The hard disk suspension according to the present invention is a component that supports a magnetic head of a hard disk drive.
FIG. 2 is a schematic cross-sectional view of an example of a hard disk suspension according to the present invention.
As shown in FIG. 2, the suspension for a hard disk according to the present invention includes a metal substrate 10 serving as a spring, and a polyimide pattern formed on the metal substrate 10 using the polyimide pattern forming method according to the present invention. An insulating layer 20, a copper wiring layer 30 provided on the insulating layer 20, and a wiring protective layer in which the copper wiring layer 30 is a polyimide pattern formed by using the polyimide pattern forming method according to the present invention. The structure is covered by 40.

In the above example, both the insulating layer 20 and the wiring protective layer 40 are polyimide patterns formed by using the polyimide pattern forming method according to the present invention. Only the kana may be a polyimide pattern formed by using the polyimide pattern forming method according to the present invention. As the wiring protective layer 40, an acrylic resin or the like can also be used.
As the metal substrate 10, a metal foil having spring-like elasticity such as stainless steel or stainless steel subjected to surface treatment is usually used. When the thickness of the metal substrate 10 used is 50 μm or less, especially 20 μm to 1 μm, the followability to the magnetic disk is improved and combined with the polyimide pattern formed using the polyimide pattern forming method according to the present invention. When used, warpage can be further reduced and flatness can be improved.

  If the polyimide pattern used in the suspension for a hard disk according to the present invention satisfies the characteristics required for the polyimide pattern formed by using the polyimide pattern forming method according to the present invention, a suspension exhibiting good characteristics can be obtained.

General examples of manufacturing the suspension include the following. First, a polyimide pattern is formed in a desired shape on a stainless steel foil (20 μm) as the metal substrate 10 using the polyimide pattern forming method according to the present invention, and a substrate provided with the insulating layer 20 is obtained. Next, a seed layer such as copper or nickel is formed on the entire surface of the obtained substrate by sputtering. Thereto, a negative resist solution is applied or a negative dry film resist is laminated, and a negative resist layer is formed on the substrate. Thereafter, exposure and development are performed, and an opening is provided only at a site where a copper wiring is to be formed.
Next, after copper plating is performed on the opening in the shape of the wiring, the resist is peeled off. Thereafter, the back surface of the substrate is masked, and the copper wiring and the surface layer of the seed layer are etched using a dilute hydrochloric acid aqueous solution or the like. Here, when the portion where the seed layer is exposed is completely removed, the substrate on which the independent copper wiring layer 30 is formed is obtained. Next, on the board | substrate with which the said copper wiring layer was formed, a polyimide pattern is formed in a desired shape using the polyimide pattern formation method which concerns on this invention, and the wiring protective layer 40 is formed.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be specifically described with reference to examples.
(Production Example 1)
4.20 g (6 mmol) of 4,4′-diaminodiphenyl ether was put into a 50 ml three-necked flask, dissolved in 5 ml of dehydrated N-methyl-2-pyrrolidone (NMP), and cooled in an ice bath under a nitrogen stream. While stirring. Pyromellitic dianhydride 1.31 g (6 mmol) was added little by little, and after the addition was completed, the mixture was stirred in an ice bath for 5 hours, and the solution was reprecipitated with dehydrated diethyl ether. The product was dried at room temperature under reduced pressure for 17 hours to obtain 2.11 g (polyimide precursor 1) of a white solid.

(Example 1)
A 20 wt% dimethylacetamide solution of the polyimide precursor 1 obtained in Production Example 1 is bar-coated on SUS304 (manufactured by Nippon Steel Corporation) with a thickness of 20 μm, and is applied so as to be 18 ± 2 μm after drying. Then, it was dried at 80 ° C. for 30 minutes in a hot air circulating oven. Thereafter, an alkali developing type dry film resist 302J38E (manufactured by Nichigo Morton) having a thickness of 38 μm is decompressed to 0.5 Mpa with a vacuum laminator, and left at a temperature of 70 ° C. on the surface of the hot plate at room temperature for 15 minutes to form a polyimide precursor film. A substrate having a negative resist film formed thereon was prepared.
Next, using a manual exposure apparatus (manufactured by Dainippon Screen Co., Ltd., MA-1200), exposure is performed at 50 mJ / cm ² (i-line conversion) through a photomask on which a desired pattern is drawn, and 0.8 wt%. The negative resist and the polyimide precursor layer are developed simultaneously using a conveyor type spray development apparatus using a tetramethylammonium hydroxide (TMAH) aqueous solution (liquid temperature 25 ° C.), then rinsed with distilled water and heated. Air-dried to obtain a pattern in which a negative resist and a polyimide precursor layer were laminated.

The board | substrate with which the pattern with which the negative resist layer and polyimide precursor layer obtained by said method were laminated | stacked was heated at 200 degreeC for 4 minutes with the conveyor oven.
The sample was immersed in a stripping solution prepared at a mixing ratio of 9: 1: 90 2-aminoethanol: surfinol 104A (manufactured by Nissin Chemical Industry): distilled water at 60 ° C. for 7 minutes, and then with distilled water. Rinse was performed, and only the negative resist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 2)
The substrate on which a pattern obtained by laminating a negative resist layer and a polyimide precursor layer, obtained in the same manner as in Example 1, was heated at 220 ° C. for 4 minutes in a conveyor oven.
The sample was immersed in ethanolamine heated to 75 ° C. for 7 minutes, rinsed with distilled water, and only the negative resist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 3)
Instead of the 20 wt% dimethylacetamide solution of the polyimide precursor 1 used in Example 1, a solution (resin composition) in which dimethylpiperidine was added so that the addition amount was 5 wt% with respect to the weight of the polyimide precursor 1 Except having used 1), it carried out similarly to Example 1, and created the board | substrate with which the negative resist layer was formed on the polyimide precursor layer and the said polyimide precursor layer. Further, in the same manner as in Example 1, a pattern in which a negative resist layer and a polyimide precursor layer were laminated was obtained.

The board | substrate with which the pattern with which the negative resist layer and polyimide precursor layer obtained by said method were laminated | stacked was heated at 170 degreeC for 4 minutes with the conveyor type oven.
The sample was immersed in a stripping solution prepared at a mixing ratio of 9: 1: 90 2-aminoethanol: surfinol 104A (manufactured by Nissin Chemical Industry): distilled water at 60 ° C. for 3 minutes, and then with distilled water. Rinse was performed, and only the negative resist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

Example 4
The substrate on which a pattern obtained by laminating a negative resist layer and a polyimide precursor layer obtained in the same manner as in Example 3 was heated at 200 ° C. for 4 minutes in a conveyor oven.
The sample was immersed in ethanolamine heated to 60 ° C. for 7 minutes, rinsed with distilled water, and only the negative resist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 5)
Instead of dimethylpiperidine used in Example 3, a solution in which 1,4-diazabicyclo [2,2,2] octane was added so that the addition amount was 5% by weight with respect to the weight of polyimide precursor 1 was obtained. A substrate having a polyimide pattern formed on a SUS foil was prepared in the same manner as in Example 4 except for the (resin composition 2) used, and a good polyimide pattern was obtained under the same conditions.

(Example 6)
A substrate on which a pattern obtained by laminating a negative resist layer and a polyimide precursor layer obtained in the same manner as in Example 5 was heated at 200 ° C. for 4 minutes in a conveyor oven.
The sample was immersed in ethanolamine heated to 60 ° C. for 7 minutes, rinsed with distilled water, and only the negative resist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

  About Examples 3-6, the temperature which carries out the imidation reaction for changing the solubility of a polyimide precursor may be reduced by adding the basic substance which is a compound which accelerates | stimulates imidation to a polyimide precursor. Therefore, in the step of reducing the solubility of the polyimide precursor layer in the basic solution, the heat treatment temperature can be lowered, and damage to the substrate or the like can be minimized.

<Test example; thermosetting temperature>
The polyimide precursor 1 and the resin composition 1 were each spin-coated on a chromium-plated glass plate to a final film thickness of 2 μm and dried on a hot plate at 100 ° C. for 2 minutes. The infrared spectrum was measured for this coating film using IR-610 manufactured by JASCO Corporation and HOTPLATE EC-1200 manufactured by ASONE Co., Ltd. while heating from room temperature to 350C at 5C / min.
The spectrum derived from the precursor disappeared with heating, and a peak derived from polyimide generated by heating appeared. In order to confirm the progress of imidization, when the peak area of 1663 cm ⁻¹ derived from the precursor before the measurement was set to 1, the amount of decrease in the peak area in the heating process was converted into the imidation rate and plotted. (The state before measurement was 0% imidation, and the time when the peak completely disappeared was taken as 100% imidation.)
The result is as shown in FIG. The resin composition 1 was found to have a decrease in the precursor at a lower temperature than the polyimide precursor 1 due to the effect of the addition of amine.

(Example 7: suspension for hard disk)
SUS304 HTA foil made of Nippon Steel with a thickness of 20 μm—a laminate made of copper alloy foil (NK-120) made of Japan Energy with a thickness of 10 μm polyimide—with a ferric chloride solution using a metal working resist. The Cu surface was etched into the desired shape. The substrate obtained by peeling the resist is laminated with an alkali development type dry film resist for polyimide layer etching, exposed to ultraviolet rays through a mask having a desired shape, and dried with a 1 wt% aqueous solution of Na ₂ CO _3. The resist was developed. Thereafter, the polyimide layer was etched, and the dry film resist was peeled off with a 3 wt% NaOH aqueous solution. In this way, the insulating layer was wet etched into a desired shape, and a polyimide patterned into the desired shape as an insulating layer was sandwiched on the foil to obtain a substrate on which copper wiring was formed.
On the substrate, (resin composition 1) obtained in Example 3 was bar-coated, applied to a thickness of 18 ± 2 μm after drying, and dried at 80 ° C. for 30 minutes in a hot air circulating oven. Thereafter, an alkali development type dry film resist 302J38E (manufactured by Nichigo Morton) having a thickness of 38 μm is decompressed to 0.5 Mpa with a vacuum laminator, and left at a temperature of 70 ° C. on the surface of the hot plate at room temperature for 15 minutes to form a polyimide precursor film. A substrate having a negative resist film formed thereon was prepared.
Next, using a manual exposure apparatus (manufactured by Dainippon Screen Co., Ltd., MA-1200), exposure is performed at 50 mJ / cm ² (i-line conversion) through a photomask on which a desired pattern is drawn, and 0.8 wt%. The negative resist and the polyimide precursor layer are developed simultaneously using a conveyor type spray developing apparatus using an aqueous tetramethylammonium hydroxide (TMAH) solution (liquid temperature 25 ° C.), and then rinsed with distilled water and heated. It was air-dried to obtain a pattern in which a negative resist layer and a polyimide precursor layer were laminated.

The substrate on which the pattern in which the negative resist layer and the polyimide precursor layer were laminated was heated at 170 ° C. for 4 minutes in a conveyor oven.
The sample was immersed in a stripping solution prepared at a mixing ratio of 9: 1: 90 2-aminoethanol: surfinol 104A (manufactured by Nissin Chemical Industry): distilled water at 60 ° C. for 3 minutes, and then with distilled water. Rinse was performed, and only the negative resist pattern was peeled off. Thereafter, heat treatment was performed at 350 ° C. for 60 minutes in a nitrogen stream to obtain a substrate on which a polyimide pattern was formed as a wiring protective layer.
Thereafter, the SUS foil was etched into a desired shape with a ferric chloride solution using a metal working resist to obtain a hard disk suspension.

(Example 8: Hard disk suspension)
SUS304 HTA foil made of Nippon Steel with a thickness of 20 μm—a laminate made of copper alloy foil (NK-120) made of Japan Energy with a thickness of 10 μm polyimide—with a ferric chloride solution using a metal working resist. The Cu surface was etched into the desired shape.
On the substrate, (resin composition 1) obtained in Example 3 was bar-coated, applied to a thickness of 18 ± 2 μm after drying, and dried at 80 ° C. for 30 minutes in a hot air circulating oven. Thereafter, an alkali development type dry film resist 302J38E (manufactured by Nichigo Morton) having a thickness of 38 μm is decompressed to 0.5 Mpa with a vacuum laminator, and left at a temperature of 70 ° C. on the surface of the hot plate at room temperature for 15 minutes to form a polyimide precursor film. A substrate having a negative resist film formed thereon was prepared.
Next, using a manual exposure apparatus (manufactured by Dainippon Screen Co., Ltd., MA-1200), exposure is performed at 50 mJ / cm ² (i-line conversion) through a photomask on which a desired pattern is drawn, and 0.8 wt%. The negative resist and the polyimide precursor layer are developed simultaneously using a conveyor type spray developing apparatus using an aqueous tetramethylammonium hydroxide (TMAH) solution (liquid temperature 25 ° C.), then rinsed with distilled water and heated. It was air-dried to obtain a pattern in which a negative resist layer and a polyimide precursor layer were laminated.
The substrate on which the pattern in which the negative resist layer and the polyimide precursor layer were laminated was heated at 170 ° C. for 4 minutes in a conveyor oven.
The sample was immersed in a stripping solution prepared at a mixing ratio of 9: 1: 90 2-aminoethanol: surfinol 104A (manufactured by Nissin Chemical Industry): distilled water at 60 ° C. for 3 minutes, and then with distilled water. Rinse was performed, and only the negative resist pattern was peeled off. Thereafter, heat treatment was performed at 350 ° C. for 60 minutes in a nitrogen stream to obtain a substrate on which a polyimide pattern was formed as a wiring protective layer.

The substrate was laminated with an alkali developing dry film resist for polyimide layer etching, exposed to ultraviolet light through a mask having a desired shape, and the dry film resist was developed with a 1% by weight aqueous solution of Na ₂ CO ₃ . Thereafter, the polyimide layer was etched, and the dry film resist was peeled off with a 3 wt% NaOH aqueous solution. In this way, the insulating layer is wet-etched to the desired shape, and the copper wiring is formed on the SUS foil with the polyimide patterned in the desired shape as the insulating layer, and further the polyimide pattern is formed thereon A finished substrate was obtained.
Thereafter, the SUS foil was etched into a desired shape with a ferric chloride solution using a metal working resist to obtain a hard disk suspension.

It is process drawing which shows an example of the formation method of the polyimide pattern which concerns on this invention. It is a typical sectional view of an example of a suspension for hard disks concerning the present invention. It is a graph which shows the relationship between the thermosetting temperature in the polyimide precursor 1 and the said resin composition 1, and the imidation ratio of a polyimide precursor.

Claims (20)

The following steps (A) to (F);
(A) forming a polyimide precursor layer on the substrate;
(B) forming a negative resist layer on the polyimide precursor layer;
(C) a pattern exposure step for selectively exposing the negative resist layer;
(D) a development step of selectively removing and patterning the underlying polyimide precursor layer after or simultaneously with the development of the negative resist layer;
(E) reducing the solubility in a basic aqueous solution or a water-soluble basic substance by at least partially imidizing the patterned polyimide precursor layer;
(F) A method for forming a polyimide pattern, comprising: a peeling step of peeling the patterned negative resist layer using a basic aqueous solution or a water-soluble basic substance.   Furthermore, (G) The formation method of the polyimide pattern of Claim 1 which has the process of polyimidizing the said patterned polyimide precursor layer.   The formation method of the polyimide pattern of Claim 1 or 2 which contains the compound which accelerates | stimulates imidation in the said polyimide precursor layer in the said (A) process.   The method for forming a polyimide pattern according to claim 3, wherein the compound that promotes imidization is an amine.   The method for forming a polyimide pattern according to claim 4, wherein the amine is an aliphatic amine.   The said polyimide precursor layer in the said (A) process WHEREIN: The compound which accelerates | stimulates imidation with respect to 100 weight part of polyimide precursors contains 0.1 to 40 weight part. A method for forming a polyimide pattern according to claim 1.   The formation method of the polyimide pattern in any one of Claims 1 thru | or 6 whose linear thermal expansion coefficient of the obtained polyimide pattern is 1 ppm / degrees C-40 ppm / degrees C.   The method for forming a polyimide pattern according to any one of claims 1 to 7, wherein the resultant polyimide pattern has a hygroscopic expansion coefficient of 1 ppm /% RH to 40 ppm /% RH.   The method for forming a polyimide pattern according to claim 1, wherein in the (F) peeling step, the negative resist layer is peeled off with a composition containing an amine.   The said (F) peeling process WHEREIN: The formation method of the polyimide pattern of Claim 9 whose composition containing the said amine is the aqueous solution containing an amine.   The method for forming a polyimide pattern according to claim 9 or 10, wherein the amine in the composition containing the amine in the (F) peeling step is an aliphatic amine.   The method for forming a polyimide pattern according to claim 9, wherein the amine in the composition containing the amine in the (F) peeling step has a structure having one or more hydroxyl groups in the molecule. .   The method for forming a polyimide pattern according to any one of claims 10 to 12, wherein in the (F) peeling step, the amine-containing aqueous solution has a concentration of amine to water of 0.1 wt% to 30 wt%. .   The method for forming a polyimide pattern according to claim 1, wherein in the (F) peeling step, the negative resist layer is peeled off at a temperature of the amine-containing composition of 0 ° C. or higher and 100 ° C. or lower.   The step (E) is a pre-resist heating step for heating the substrate on which the patterned negative resist layer and the patterned polyimide precursor layer are formed, and the heating temperature is 100 ° C. to 250 ° C. The formation method of the polyimide pattern in any one of Claims 1 thru | or 14 which is degreeC.   The method for forming a polyimide pattern according to claim 1, wherein in the step (B), the negative resist layer is formed using a dry film resist.   An article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member having a polyimide pattern formed by using the polyimide pattern forming method according to any one of claims 1 to 16.   The article according to claim 17, wherein the polyimide pattern is formed on stainless steel or surface-treated stainless steel.   The article according to claim 18, wherein a thickness of the stainless steel or the stainless steel subjected to the surface treatment is 1 μm to 50 μm.   A hard disk suspension having a polyimide pattern formed by using the method for forming a polyimide pattern according to claim 1.

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